The present invention relates to a self-centering sealing bush unit for sealing reciprocating machine parts, particularly pistons of fluid-supplying pumps, as well as to a machine such as a fluid-supplying pump provided with such sealing bush.
Known sealing bush units include a sealing bush with an inner diameter which is greater than the outer diameter of a piston, whereby forming an annular sealing gap. Working pressure acts upon the rear side of the sealing bush opposite to the sealing gap over a part of its length, and the bush is radially movable relative to the piston. The sealing bush has a flat face extending normal to the piston axis and provided for axial abutment of the bush. One such sealing bush unit is disclosed in German Pat. No. 2,328,963. The sealing bush unit of this patent has a self-centering sealing bush which is axially pressed against an intermediate sealing disk with the aid of an axially acting spring. The intermediate sealing disk abuts with its spherical face against a relatively movable insert. The center of the sphere of the spherical face serving for abutment of the intermediate sealing disk lies in or adjacent to a center of the sealing bush. When the sealing bush unit is designed in accordance with the present invention, a contact-free self-centering of the sealing bush with a minimum of force consumption is attained. Because of the radially and angularly adjustable support of the intermediate sealing disk, the sealing bush corresponds to the movement of the reciprocating parts and can deform freely over its entire length. This construction is used in practice. For unobjectionable operation of the above-described sealing bush unit, it is, however, necessary to provide a spring device and an intermediate sealing disk having a spherical face. Moreover, this construction cannot be advantageously utilized when the pump is equipped with several pistons, inasmuch as the distances between the individual sealing bushes can be changed under the action of temperature.